This paper subjects to critical analysis four common arguments in the sociopolitical theory literature supporting the cultural nationalist thesis that liberal democracy is viable only against the background of a single national public culture: the arguments that (1) social integration in a liberal democracy requires shared norms and beliefs (Schnapper); (2) the levels of trust that democratic politics requires can be attained only among conationals (Miller); (3) democratic deliberation requires communicational transparency, possible in turn only within a shared national public culture (Miller, Barry); and (4) the economic viability of specifically industrialized liberal democracies requires a single national culture (Gellner). I argue that all four arguments fail: At best, a shared cultural nation may reduce some of the costs liberal democratic societies must incur; at worst, cultural nationalist policies ironically undermine social integration. The failure of these cultural nationalist arguments clears the way for a normative theory of liberal democracy in multinational and postnational contexts.